1. Field of the Invention
This invention relates to flux compositions for use in the production of iron and steel and more particularly to acid and basic flux compositions for use in obtaining slag fluidity in the production of iron and steel.
2. Description of the Prior Art
In the process of refining metal for the use in the production of iron or steel difficulties have been encountered in the past in separating the impurities, which are chemically combined and physically mixed with the metal, from the molten metal in the furnace. In order to purify the metal ore, the metal has been separated from the impurities in the metal ore by fusion. To render the impurities more easily fusible, fluxing agents have been added to the molten metal in the furnace or converter through the refining process. It has been a further function of fluxing agents to reduce the viscosity of slag and increase slag fluidity.
Initially, many different fluxing agents were employed to remove the impurities contained in the ores which were to be refined for the formation of slag and further to increase the fluidity of the slag for its separation from the molten metal. For example, U.S. Pat. No. 91,324 discloses the use of fluorspar and horse manure with wood and carbon in combination for the purpose of smelting iron, gold, silver, and copper ores in the manufacture of iron, steel, and brass. U.S. Pat. No. 120,099 discloses a flux composed of broken glass, pulverized charcoal, and calcined shells combined with soda ash or carbonate of soda and silicous sand to be used in the reduction of ores in refining of metals. U.S. Pat. No. 145,580 teaches fluxes for treating ores and metals composed of borax with silica in the form of infusorial earth or silicous diatoms, and chlorine of sodium together with the necessary quantity of powdered fluorspar or dolomite compressed into grains, pellets, or bricks as desired. The flux composition causes the slag to be very fluid and aids in removing deleterious materials, such as phosphorus and sulfur.
U.S. Pat. No. 465,314 provides a process of manufacturing steel wherein phosphorus, sulfur, and other impurities are removed from the iron and other ores by the employment of chemical products introduced into a smelting furnace. The chemical composition employed in the steel making furnace to remove the impurities in the metal includes a mixture of silica, alumina, iron oxide, phosphoric acid, carbonate of lime, and manganese oxide.
More recently fluxing compositions for use in metallurgical purification operations have been prepared to include fluorspar, magnesium, and calcium compounds as found in the form of dolomite and iron oxides to lower the viscosity of the slag material produced. In the steel making process as taught in U.S. Pat. No. 3,645,719 calcium oxide and magnesium oxide in the form of dolomite are prereacted with iron oxide to form shaped bodies of dicalcium ferrite. The dicalcium ferrite bodies are added to the furnace of the steel making process as a basic slag forming ingredient for the improved removal of phosphorus and sulphur. Great Britain Pat. No. 1,258,102 teaches artificial self-fluxing slag forming agents made by mixing the ingredients in a fine powder form and baking the ingredients into lumps which are then blown into the converter for forming slag. The first slag forming agent is comprised of a mixture of calcium oxide, ferric oxide, and silica. The second slag forming agent includes a mixture selected from aluminum oxide, calcium fluoride, titanium oxide, magnesium oxide, manganese oxide, and alkali metal oxides. In addition, U.S. Pat. No. 3,309,196 provides a fluxing agent for the purpose of making slags more fusible in the reduction of oxidized iron material. An acid flux is provided as pellets in agglomerated particulate form for metallurgical fluxing consisting essentially of calcium oxide in the form of lime, sodium oxide in the form of soda ash, aluminum oxide, and silica in the form of sand. Also, a basic fluxing agent is provided in pellets of agglomerated particulate form consisting essentially of lime, aluminum, soda ash, silica, and iron oxide.
Generally, it has been the practice to employ fluorspar as a source of calcium fluoride, CaF.sub.2, as a fluxing agent to make slag more fusible in the purification process. It has been found, however, the fluorspar when used as a fluxing agent combines with the impurities in the molten metal to produce slag that corrosively reacts with the refractory material composing the lining of the furnace of the converter thereby reducing the furnace lining life. There is need for a flux composition that protects the refractory material composing the furnace lining, of a converter from corrosive action of the slag. Further, there is need to provide a fluidizing flux having a composition which increases the fluidity of slag without the presence of florides in the flux composition.